Under-water speaker

W50 GMM Underwater Loudspeaker

1. Brief Introduction
Giant Magnetostrictive Material (short as GMM)， a kind of grain oriented crystal，  is a kind of smart material that can change electric/magnetic engergy into mechanical/sonic energy. When exerting a dynamic magnetic field to the rod (this is done by an electric current flowing through a solenoind with the GMM rod in the certer), the rod will vibrate or  displace periodically, the displacement is tens or even a hundred times that of traditional material. Because of its advantages of big displacement, high output force and power, it was adopted for large power underwater emitting sonar by U.S. navy. 
An underwater loudspeaker usually requires a powerful transducer of big output force, big power and broad bandwidth, as well as waterproof and compressive pressure resistance. Obviously, it is difficult for the traditional loudspeaker with a paper basin to perform this hard underwater work.
Based on both the patented crystal material of GMM and accumulated experience on research & development of transducer, our company successfully has invented this new kind of W50-type underwater loudspeaker which is in a position of undertaking underwater broadcasting. With a powerful internal sonic transducer, it can drive the sounding board to  vibrate which is in turn be effectively coupled into water as shown in the schetch drawing below. The wonderful product can be used in many fields such as music playing and broadcasting for swimming games, recreation, underwater ballet etc., suitable for use in large or small swimming pools such as a family swimming pool. Also can ben used in underwater communications, underwater breeding, etc.
 

The above diagram shows how the GMM underwater loudspeaker works: driving by a power amplifier, the GMM transducer of broad bandwidth and big power changes the music signals ito audio vibration that pushes a non-metal sounding board to be vibrated, and finally the audio vibration is transferred to the water to be heard by man inside water.

2. Features
Advantageous in high sensitivity, big power, perfect sound effect, low voltage, high safety and reliability, enclosed and waterproof design, the GMM underwater loudspeaker thoroughly resolves the problem of the traditional loudspeaker being unable to be used under the water. And also it can work properly under high pressure as well as varied  temperature under the water. 

3. Technical Parameters
 

• Impedance: 4 Ω
• Response frequency: 200～10000Hz
• Rated power: RMS 25W
• Dimension: 245(D)x119(H)mm
• Weight: 3.4 kilogram

4. Device preparation, connection and usage
According to both the size of your swimming pool and your request of sound level, you may purchase one or more pieces of GMM underwater loudspeaker. Generally speaking, 1-2 pieces are enough for a family swimming pool; while 4 or more pieces are suggested to be used for large swimming pools. In this occasion, speakers should be installed inside four different walls of the swimming pools or in the four corners of a swimming pool.
To form your underwater, a suitable amplifier and sound sources such as CD, DVD players, etc are also needed which are available in an audio shop. As for installation of only one piece underwater speaker system, you need an amplifier with a rated power by over 100W; while as for installation of underwater system composed of more than one piece of speakers, the reted power of the amplifier equals 100W × the number of pieces to be installed, for instance, 3 pieces system needs an amplifier with the rated power by 300 W, and the three pieces of speaker should be connected in parallel.
 

If placing the amplifier close to the swimming pool, you may purchase an ordinary AV amplifier; if placing the amplifier relatively far from the swimming pool, you may choose a constant voltage audio amplifier(such amplifier can amplify the signals by means of raising the output voltage up by 70-120V through the transformer between the lines inside the amplifier box, cables are used to transfer this comparatively high voltage signal  to a long distance and connected to a transformer near the underwater speaker, decrease the voltage in order to couple with the impedance of the speaker. If the room or place to put the amplifier is damp, then damp-proof amplifier is suggested.
After completion of the installation in one of three ways described in the following section, you need to link the underwater loudspeaker to the amplifier with duplex line with a sectional area of each no less than 2.5 square millimeters, and then covere all the lines up inside walls and under the ground so as to be clean and meet the safety requirement. Finally you can play music and appreciate it under the water. If you have a microphone, you can broadcast to people who dive in water.

5. Installation Methods
(1) wall embedded fixing and installation
Before building the swimming pool, reserve one or several square or round holes beneath the water surface with dimensions larger than that of a W50 speaker. The underwater loudspeaker should be installed inside the hole with screw bolts. Then the hole should be covered with a soft plastic net for protection.  If a swimming pool has already been built, then dig one or several holes on the wall and below the water surface, reinforce the walls of the hole to be water proof, then install the speaker in a similar way.
 

(2) corner fixing and Installation If you do not want to drill holes in the wall, you may install the underwater loudspeaker(s) with the screw bolts in the corner of the swimming pool under the water, and cover it up with a smooth protection net to protect from bumping into it and causing swimmers’ injury.
 

(3) Floating intallation
Besides two above-mentioned ways, you can install the underwater loudspeaker under the floating block which is floating on the water surface. This is the most convenient method to use a underwater speaker and also the speaker system can be easily uninstalled after use.